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clocksource: Handle negative skews in "skew is too large" messages 

[ Upstream commit e40806e9bc ]

The nanosecond-to-millisecond skew computation uses unsigned arithmetic,
which produces user-unfriendly large positive numbers for negative skews.
Therefore, use signed arithmetic for this computation in order to preserve
the negativity.

Reported-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Reported-by: Feng Tang <feng.tang@intel.com>
Fixes: dd02926994 ("clocksource: Improve "skew is too large" messages")
Reviewed-by: Feng Tang <feng.tang@intel.com>
Tested-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Paul E. McKenney 2023-06-07 11:59:49 -07:00 committed by Greg Kroah-Hartman
parent e5de968a90
commit de1dbbefac
1 changed files with 4 additions and 4 deletions
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8
kernel/time/clocksource.c
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@ -473,8 +473,8 @@ static void clocksource_watchdog(struct timer_list *unused)
/* Check the deviation from the watchdog clocksource. */
md = cs->uncertainty_margin + watchdog->uncertainty_margin;
if (abs(cs_nsec - wd_nsec) > md) {
u64 cs_wd_msec;
u64 wd_msec;
s64 cs_wd_msec;
s64 wd_msec;
u32 wd_rem;
pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
@ -483,8 +483,8 @@ static void clocksource_watchdog(struct timer_list *unused)
watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask);
pr_warn(" '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n",
cs->name, cs_nsec, csnow, cslast, cs->mask);
cs_wd_msec = div_u64_rem(cs_nsec - wd_nsec, 1000U * 1000U, &wd_rem);
wd_msec = div_u64_rem(wd_nsec, 1000U * 1000U, &wd_rem);
cs_wd_msec = div_s64_rem(cs_nsec - wd_nsec, 1000 * 1000, &wd_rem);
wd_msec = div_s64_rem(wd_nsec, 1000 * 1000, &wd_rem);
pr_warn(" Clocksource '%s' skewed %lld ns (%lld ms) over watchdog '%s' interval of %lld ns (%lld ms)\n",
cs->name, cs_nsec - wd_nsec, cs_wd_msec, watchdog->name, wd_nsec, wd_msec);
if (curr_clocksource == cs)